It is known that changing the electrical and/or electrical chemical environment of living tissue causes a modification of the growth, repair, and maintenance behavior of the tissue. The modification is carried out by subjecting the tissue to electrical voltage and current. One method of changing the electrical environment comprises the use of a 1-15 microampere constant current source across a bone fracture. Metal electrodes are used to transmit the current. Clinical evidence demonstrates acceleration of ossification or bone fracture healing. Another method of altering the electrical environment is the use of induced currents from the outside of the body via magnetic pulses from externally applied coils. The coils induce current in the conductive environment of the tissue and thereby create healing effects by altering the effective current in the tissue at the bone fracture site.
Various duty cycles and frequencies are critical in achieving bone healing in the implementation of the magnetically induced current method. Ion mobility and distance of travel across the fracture dictates the net energy required over time. Due to the restrictive nature of the implementation of the induced currents by a pulsed magnetic field, specific parameters of ON time, OFF time, and the asymmetry of the positive and negative portions of the pulse wave determine the net energy over time in any one direction. This restricts the magnetic-induced method to a very limited range which may not necessarily be biologically optimum for the particular patient's condition. The magnetic-induced method is advantageous in that the currents are induced throughout the region of the treatment, rather than confined to the fracture site. The dispersion of the current induced in the region may of necessity effect the blood flow in the region with subsequent beneficial results. Bone fracture healing is also enhanced due to the charged nature of proteins and extra cellular fluids.
Ryaby and Pilla in U.S. Pat. Nos. 4,266,533 and 4,315,503 disclose a method and apparatus for enhancing the growth, repair, and maintenance of living tissues by applying pulse wave forms of voltage and current of specific timed frequency amplitude relations to the tissue. A varying electro-magnetic field is inductively coupled through direct induction into or upon the tissue under treatment. The information furnished to the tissue is designed to influence the behavior of the non-excitable cells, such as those involved in tissue growth, repair, and maintenance.
Kraus discloses in U.S. Pat. No. 3,915,151 an apparatus for promoting healing of bone tissue with the use of a coil to produce a magnetic field within the region to be treated and sheet-like electrodes associated with the coil to produce an electrical field to influence the recovery of the structure of the damaged bone tissue.